The ability of cardiac scintigraphy with indium-lll ('1l1n)-labeled platelets to detect coronary artery thrombosis (CAT) was assessed in a canine model. Cardiac imaging and tissue distribution studies were performed shortly after administering "11In-labeled platelets to 12 dogs (group 1) with acute CAT. Four dogs (group 2) with acute CAT were studied 2 and 22 hours after administering "'In platelets. In addition, four dogs (group 3) with 24-hour-old CAT were similarly evaluated. In all group 1 animals, in vivo imaging 1-2 hours after. In platelet administration revealed intense uptake in the region of thrombus-containing left anterior descending arteries that was readily discernible from background blood pool activity. Sequential imaging of the four group 2 animals over a 22-hour period revealed no change in the scintigraphic pattern of the thrombosed arteries. In contrast, "'In platelet imaging in the four group 3 animals with 24-hour-old CAT failed to reveal enhanced activity within the region of the thrombus-containing coronary artery. In the 12 group 1 animals, the CAT accumulated 69 ± 10 (mean ± SEM) times greater activity than present in blood and 651 ± 135 times greater activity than normal left ventricular myocardium. There was 24 ± 7 times greater "'In activity in the damaged left anterior descending arteries compared with normal circumflex arteries. Similar uptake ratios were seen in group 2 animals. The 24-hour-old thrombi from group 3 animals showed no enhanced "'In uptake.
This study demonstrates that experimental acute CAT can be detected readily with "'In platelet cardiac scintigraphy. Acutely formed thrombi accumulate labeled platelets, but 24-hour thrombi do not. Serial imaging of acutely formed thrombi over 22 hours after the administration of "'In platelets shows no significant change in the scintigraphic appearance. This technique may provide a better understanding of the role of thrombosis in myocardial infarction.